This invention relates to the construction of tunnel tubes for use under rivers, bays and other bodies of water, and more particularly to improved apparatus and process of manufacture of the component parts for such tunnel tubes. Then the tubes are positioned in open-trenches on the floors of the bodies of water, the tubes are assembled from individual sections which are fabricated on land and then floated to the tunnel site where they are lowered into place. Due to their enormous size, the tunnel sections are in turn constructed of a plurality of separate modules which are individually fabricated and then assembled together.
Tunnel tubes for vehicular highways or mass-transportation systems can be on the order of one-half mile to a mile or more in length. Typically, the tunnel sections used to make up the tunnel tubes are made of steel, can be 300 to 400 feet in length, 30 to 40 feet in diameter, for example, and thousands of tons in weight. The tunnel modules in turn are the same diameter as the sections, but are a fraction of their length and weight and are easier to assemble and handle. For example, a tunnel section can be comprised of five to ten tunnel modules or more, each module being 30 to 45 feet in length.
The tunnel tubes can have a single passageway or lane for traffic, or can have several lanes. Often two tunnel sections are intimately joined together side-by-side forming a tunnel tube with four lanes or more for traffic.
The individual tunnel modules are welded or otherwise securely fixed together at the construction site into an elongated tunnel section. Where a single tunnel section is utilized, the requisite number of modules are reinforced, positioned end-to-end, and then joined together as unit. Where two tunnel sections are to be constructed as a tunnel unit, the modules are welded both end-to-end with other modules, as well as side-by-side with adjacent modules. An external framework of steel plates is positioned around the perimeter of the tunnel sections forming enclosed units. The open ends of the hollow tunnel sections are also covered with steel plates so that the sections can be floated and towed to their final positions. Either at the site where the tunnel sections are assembled, or at another site where the sections are first towed, the sections are completed internally with a concrete lining, roadways, fresh air passageways, wiring and the like. In this manner, once the tunnel sections are positioned in the trenches, most of the remaining work will involve connecting the internal structures and mechanisms together.
The construction methods and equipment used to position and lower the tunnel sections into the trench and then fasten them together underwater are known and do not form a part of this invention. A preferred method is disclosed in the article entitled "Deep-Water Tunneling Operations Tie-In with Pinpoint Accuracy", which appeared in the September, 1973 issue of "Construction Methods & Equipment", the disclosure of which is hereby incorporated by reference.
The trench is dredged and the bed is prepared while the tunnel sections are being constructed and towed into position. The tunnel sections are accurately positioned over the trench on the water surface by barges and tugboats and then weighted further with ballast and slowly lowered beneath the water into the trench. One end of each section has a large rubber gasket mounted around it and hydraulically operated jacks and locking devices are actuated to pull the sections together in the trench and securely lock them together. Since the tunnel sections are hollow and sealed, the only water which needs to be evacuated is contained in the areas between the sections. Once this is pumped out, the facing plates on the ends of the sections are removed and finishing work is done to connect the sections and complete the tunnel tube. When the tunnel sections are finally positioned and locked in place, they are covered over with fill as well as the material originally excavated from the trench.
The tunnel modules are formed from a large rectangular steel plate of about 1/4 to 9/16 inch in thickness which is rolled into a large cylinder. A cylindrically-shaped fixture is used as a form around which the cylinder is rolled. The rolling fixture (also called a "spider") is collapsible so that it can be removed later from the module.
After the module shell is formed, the shell and fixture are placed as a unit on pedestals where a supporting and bracing framework is constructed around the external surface of the shell. The shell and fixture unit is adapted to be rotated so that the external framework can be secured to it in the easiest manner. An access tower is provided for workmen so they can more easily position and secure the framework components to the shell.
Once the braces, struts and other supporting framework are fixed to the shell, the module is complete except for the external skin or surface of steel plates. The plates can be added at this time before the fixture is collapsed and removed, or afterwards when the module is being secured to other modules.
When all the modules are welded together and the external plates and end plates are welded on them forming an integral tunnel section, the section is complete and ready to be launched. Access to the tunnel sections for any further internal work is accomplished through one or more holes cut in the top thereof.
Heretofore when tunnel modules have been constructed, some problems and difficulties have been encountered in the construction process. Some of these problems relate to the rolling up of the steel shell, the rotating of the shell and fixture on the pedestals, the collapsing of the rolling fixture, the removal of the fixture from the shell, and the reassembly of the fixture for reuse. Another problem area concerns workman access from the tower to the shell for assembly of the diaphragms and support framework.
It is an object of this invention to improve the apparatus and process for fabrication of tunnel modules. It is a further object to overcome one or more of the problems and difficulties heretofore encountered in the construction of tunnel modules and sections.
The above problems and difficulties are overcome by means of the apparatus and process described and claimed herein. The apparatus and process are further shown in the appended drawings which are described below.